1. Field of Invention
This invention relates generally to a system and method for cooling the walls of industrial vessels which, through their use, are exposed to extremely high temperatures. Specifically, this invention is a means for cooling Claus units, the vessels used to produce elemental sulfur by burning hydrogen sulfide in conjunction with air and/or oxygen. Moreover, this invention relates to an improved heat recovery system for use with Claus units, sulfur recovery systems, and industrial plants.
2. Related Art
Different methods for cooling industrial vessels, such as furnaces, that are exposed to extremely high temperatures are known to the prior art. Illustrative of such methods are U.S. Pat. No. 4,235,173 issued to Sharp, U.S. Pat. No. 4,443,188 issued to Buhler, and U.S. Pat. No. 4,715,042 issued to Heggart et al. Each of the methods disclosed in the patents utilizes a liquid cooling means; however, each of the listed prior art methods is structurally constrained, functions differently than the present invention, and would not be easily applied to a Claus unit.
Like many industrial vessels, Claus units are exposed to extremely high temperatures through their use and during their life. Normal temperatures in a Claus unit can range from 2700.degree. F. to 3000.degree. F. Such extreme temperatures are usually high enough to melt the vessel walls. Needless to say, such an outcome presents a grave danger to workers within the industrial plant and may be catastrophic to the industrial plant which utilizes the vessel.
Thus, providing a cooling means which maintains the interior of the Claus unit at the required high temperature while cooling the walls of the unit to an adequate and safe level is beneficial to the prior art.
Prior art cooling means consist primarily of refractory lining attached to the interior of the Claus unit. The refractory lining insulates the walls of the unit from the extreme temperatures in the interior of the unit.
Unfortunately, the refractory lining thickness required to maintain adequate and safe temperatures in a Claus unit can be as thick as 15 inches and is very costly. The large thickness of the lining also substantially reduces the area available for use within the vessel. In addition, costly and sophisticated instrumentation is required to monitor the temperatures of the vessel and the refractory lining. Moreover, the refractory lining itself may melt if the temperature in the interior of the unit reaches a high enough level through human or mechanical error.
The use of refractory lining as a means to cool a vessel also has other disadvantages: the usable life of the vessel is reduced since heat radiates from the lining back into the vessel exposing the interior of the vessel to excess heat; the vessel may not be quickly activated or deactivated since refractory lining thermal stress then becomes a concern; and the vessel may not be quickly serviced since the refractory lining must be given a substantial amount of time to cool down prior to service.
Thus, it would be beneficial to provide a means for cooling a Claus unit which does not encounter the disadvantages of the use of refractory lining as herein stated.
In addition, as extensively practiced in the art, Claus units are normally only a part or sub-process of the overall process of an industrial plant. Normally, Claus units are utilized within industrial plants to produce elemental sulfur from gases, primarily hydrogen sulfide, that are by-products of the plants's overall process or other sub-processes. Most, if not all, of industrial plants utilize extensive and varied raw or input materials in a number of sub-processes within the overall industrial plant process. Efficient industrial plants utilize the by-products or end products of one sub-process as the raw or input materials of other sub-processes. For example, an efficient industrial plant may utilize a relatively high temperature by-product gas of one sub-process to heat an otherwise relatively cold material which requires a higher temperature for use in its relevant sub-process.
Thus, it would also be beneficial to provide a Claus unit cooling means which produces a by-product or end-product useful within the Claus process itself or elsewhere within the industrial plant process.